Nitrogen monoxide decomposition catalysts prepared from amorphous Ni-valve metal-Pd alloys

Surface-activated amorphous Ni-valve metal (Ta, Nb and Zr)-Pd alloys have been used for the decomposition of nitrogen monoxide. The alloys, which are first activated by immersion in hydrofluoric acid and subsequently oxidized by exposure to oxygen at 500 °C, show a high activity for the decomposition of nitrogen monoxide and have superior deterioration resistance. The catalytic activity of the alloy catalysts is affected by the valve metal elements. The tantalum- and niobium-containing alloy catalysts show higher activities and nitrogen formation selectivities than those of the zirconium-containing alloy. Double oxides of NiTa₂O₆ and NiNb₂O₆ are formed during the reaction at temperatures higher than 750 °C and, at the same time, the catalytic activity increases sharply. The synergistic effect of palladium and the double oxides seems to contribute to the high catalytic activity of the Ni40Ta1Pd and Ni40Nb1Pd alloys.